A display with moving or changing elements is much more effective in attracting attention than a stationary display. Flashing or varying lights, moving parts and other such motion producing effects have been used to animate display. Other types have used colored oils and similar fluid materials flowing through channels or tubes to attract attention. Such arrangements invariably use some time of pump, one for each color, and can become very complex for performing a simple task.
As examples, U.S. Pat. No. 3,413,744 shows a fluid type system in which flow of colored fluid to individual chambers is controlled by a fluid logic system driven by an external pressure source. U.S. Pat. No. 3,405,464 shows selective control of fluid flow to elements of a display character by a manometer type system, using an external pressure source for power. U.S. Pat. No. 2,645,048 is for a simpler type of display in which fluid is pumped through a continuous length of tubing formed into a me, the advancing fluid simulating the progressive writing of the name. These patents are representative of various methods of controlling fluid flow for display purposes, but all require considerable associated apparatus for their operation.